A rough guide to abdominal aortic aneurysms

By Nick Harper

The abdominal aorta

T12

L4

• Normal diameter:16 to 22mm

• Aneurysm: ≥50% increase

• Rupture: 8000 deaths in total per year in the UK

•1.5% of deaths in men between 65 and 85

•(Sakalihasan, N. et al. 2005)

Prevalence

• Men between 3 to 8%• Women between 0.5 to 1.5%

(Wilmink, A.B. & Quick, C.R., 1998).

For the ≥50 age group

(Vardulaki, K.A. et al. 2000)

Types of aneurysm

Thrombus

What causes AAAs?•genetic predisposition

•Marfans•Loyes-Dietz•Ehlers Danlos

•Atherosclerosis

•haemodynamic strain

•thrombus formation

•enzymatic degradation

•Vasculitis

•Syphilis

•cystic medial necrosis

•trauma

The aortic wall:

Elastin Lamellae decrease from thoracic to abdominal

Proteases

Adventitia

Media

Thrombus

Elastin

Collagen VSMC

P

P

P

TIMP

Neutrophils

1

2 3

4

MMPs - Matrix Metalloproteinases

TIMPs - Tissue inhibitors of MMPs

(Allaire, E. et al. 2009).

Detection

ImagingUltrasoundinitial assessment and follow up

Quick, easy, cheap & no radiation.

Can measure the size of the aorta to the nearest 3mm Doppler scans allow visualization of blood flow

CTif considering a surgical procedure

More accurate, high sensitivity and specificity

3D reconstruction CT angiography

BUT! cost, time and radiation exposure

Aortic Wall

Lumen Thrombus

Open RepairProcedure1. general anaesthesia.2. midline incision3. AAA is identified4. Proximal control – Clamp the Aorta

(preferably below the renal arteries)5. Distil Control – Clamp the common

iliac arteries6. The aneurysm is opened and any

thrombus is removed7. A graft is anastamosed to either

end of the affected section8. Clamps are removed and blood flow

is returnedMortality rates following elective open repair:4.6% 30 days post-op6.3% after 4 Years (AAA related mortality only)

•Bilateral femoral artery access via Seldinger technique

•Aortogram

•Catheter insertion

•Deployment of main body

•Insertion and deployment of contralateral limb

Endovascular aortic aneurysm repair (EVAR)

Deployment

CatheterEVAR stent graft

Main body

Contralateral limb

Mortality rates following elective EVAR

•1 to 2% 30 days post-op•3.5% after 4 Years (AAA related mortality only)

Endoleak

Aortogram

Transverse CT

Classification

Comparing EVAR to open repairAdvantages No difference Disadvantages

Can be performed without general anaesthesia

Long term all cause mortality

Higher rates of complication

Shorter postoperative stay by on average 5 days

Graft stenosis or infection Secondary intervention more likely to be required. This is successful in 84% of cases

Lower 30 day mortality (odds ratio 0.46)

More expensive ≈ £12,000 for EVAR compared to ≈ £10,000 for open repair

Lower long term aneurysm related mortality (hazard ratio 0.39)

(Lovegrove, R.E. et al. 2008) In younger patients open repair may be a longer term solution

RupturesEMERGENCY!

• 100% mortality if untreated!

• Sudden & severe abdominal pain

• radiation to back and groin.

• Shock

• ΔΔ acute pncreatitis

Acute management•Call a vascular surgeon or anaesthetist

•wide bore IV access

•If the shock is severe give blood

•keep systolic BP ≤100mmHg

•ECG & blood amylase/lipase

•Crossmatch blood

•Take the patient to theatre for open repair

Size of AAA Risk of rupture per year4cm or less Low risk 4 - 5cm 1 in 100 per year5 - 6cm 1 in 12 per year6 - 7cm 1 in 6 per yearOver 7cm 1 in 4 per year or higher

Prevention• Control of risk factors

• Ultrasound screening roughly halves AAA related mortality in men over the age of 65. (Fleming, C. et al.2005).

• UK AAA screening program• Starting spring 2009. • For men aged 65 years and older.

• http://aaa.screening.nhs.uk/.

References• Allaire, E., Schneider, F., Saucy, F., Dai, J., Cochennec, F., Michineau, S., Zidi,

M., Becquemin, J-P., Kirsch, M. & Gervais, M. (2009) New insight in aetiopathogenesis of aortic diseases. European Journal of Vascular & Endovascular Surgery. 37(5), 531-537

• Lovegrove, R.E., Javid, M., Magee, T.R. & Galland, RB (2008) A meta-analysis of 21178 patients undergoing open or endovascular repair of abdominal aortic aneurysm. british journal of surgery. 95(6), 677-684

• Sakalihasan, N., Limet, R. & Defawe, O D. (2005) Abdominal aortic aneurysm. Lancet. 365(9470), 1577-1589

• Vardulaki, K.A., Walker, N.M., Day, N.E., Duffy, S.W., Ashton, H.A. & Scott, R.A. (2000) Quantifying the risks of hypertension, age, sex and smoking in patients with abdominal aortic aneurysm. British Journal of Surgery. 87(2), 195-200